Although applicable to any kind of aircraft or spacecraft or the like, the present disclosure and the problem on which it is based will be explained in greater detail with reference to fuselage shells of commercial aircraft.
A fuselage shell of a modern airplane consists of a rigid framework of stiffening elements that is covered by a metal or composite skin. The framework normally comprises a series of frames bent into a circumferential direction according to the shape of the fuselage cross section and a plurality of longitudinal stringers that are joined to the frames. A typical fuselage is divided in the longitudinal direction into so-called frame stations, each of which contains one frame that is built up of several frame segments. Typically 4 to 8 of such frame segments are coupled together in the circumferential direction to form one frame. Even though there are various types of frames with different cross sectional shapes, often these are formed from sheet metal in a roll forming process.
The document DE 10 2006 040 298 B4 discloses a lightweight structural component, in particular for an aircraft, having a skin panel and stiffening elements arranged on it. The stiffening elements comprise two substantially parallel solid web elements, which are each attached to the skin panel at a respective foot portion and are connected with each other at a respective head portion by a number of connection elements that extend from one web element to the other web element such that openings are left in between the connection elements. This specific configuration of a stiffening element with two solid web elements and a roof-like framing saves weight in case it is used as a stringer or frame compared to a closed stiffening element of the same cross section. In addition, the space between the two web elements can be utilized for various purposes, e.g. for cable routing.